Immunogenicity of heparin-binding hemagglutinin expressed by Pichia pastoris GS115 strain

Objective(s): Heparin-binding hemagglutinin (HBHA), a mycobacterial cell surface protein, mediates adhesion to nonphagocytic cells and the dissemination of Mycobacterium tuberculosis (M. tuberculosis) from the site of primary infection. Superior expression systems are required to obtain abundant M. tuberculosis proteins for the purpose of diagnosing M. tuberculosis infection or for the immunization. Here, HBHA was expressed by Pichia pastoris (P. pastoris) GS115 strain , and the immunogenicity of HBHA was evaluated. Materials and Methods: The HBHA gene of M. tuberculosis was cloned into the pPIC9K plasmid, which was good for electroporation into P. pastoris GS115 strain. Unlabeled HBHA protein was purified using a Sepharose CL-6B column, and its expression was confirmed using anti-HBHA polyclonal antibody from mouse serum. We injected C57BL/6 mice with HBHA/ dimethyldioctadecylammonium/trehalose 6,6′-dibehenate (HBHA/DDA/TDB) to investigate the immunogenicity of this potential vaccine. Results: The results demonstrated that HBHA/DDA/TDB has the ability to induce high levels of HBHA-specific IgG antibody and its subclasses, as well as interferon-gamma, compared with injection of phosphate-buffered saline, DDA/TDB alone and Bacillus Calmette-Guérin (BCG) controls (P<0.05). Moreover, the ratio of IgG2a/IgG1 of the HBHA/DDA/TDB group was higher than that of the BCG group (P<0.05). Conclusion: HBHA with no label has excellent immunogenicity, and is suitable for evaluating the effectiveness to prevent M. tuberculosis infection.